Computers are widely used: to store and find data, to move data from storage to a data manipulation area, to carry out the modification and processing of data necessary to transform such data into useful information, to output selected data to an output device, and to move new or modified data to data storage devices.
The definition of the process and apparatus employed for the data management tasks just enumerated is commonly called a database model. A database is a repository for data with a defined organizational scheme, subject to defined processes to manipulate the data and defined constraints to assure data integrity. Therefore, the database model describes the logical or physical structure and the method for processing the data.